The present invention relates to a heat exchanger for the coolant circuit of an internal combustion engine. The heat exchanger includes an upper water tank, a lower water tank that is connected to a return line, heat exchanger tubes that extend between the upper and lower water tanks, and an air-withdrawal line that extends from the upper water tank into the region of the lower water tank.
It is known to provide a so-called by-pass line in a heat exchanger that is designed as a radiator. Air that accumulates in the upper water tank is withdrawn via this by-pass line. It has been attempted to increase the withdrawal efficiency by disposing between the heat exchanger register and the upper water tank a partition that has a relatively small opening. The by-pass line has a larger, free, cross-sectional area than does the opening in the partition. Unfortunately, this arrangement has a relatively low withdrawal efficiency. Where there is a greater yield of air in the cooler, there is a danger that the air that is present can no longer be completely removed, so that the cooling capacity decreases.
It is also known pursuant to a different construction to make the free, cross-sectional area of the opening in the partition greater than that of the by-pass line. This is an attempt to have the air bubbles from the heat exchanger, which is similarly designed as a radiator, pass more quickly into the upper water tank, and to have the radiator filled more quickly with coolant. However, this arrangement also provides only a low withdrawal capacity or efficiency, so that when the air yield is great, the radiator is filled with air and can no longer bring about a cooling effect. Since gas and air bubbles contained in the coolant also reduce the efficiency of radiators that are disposed in the coolant circuit of internal combustion engines, it is an object of the present invention to provide a heat exchanger that assures an improved, and especially a more uniform, transmission of heat.